1. Field of the Invention
This invention concerns rotary drilling systems, in general. More specifically, it deals with such a system that includes a torque meter for measuring dynamic torque while drilling, and it relates to a combination that provides a system for indicating the time period of oscillations in the torque that is being applied during drilling operations.
2. Description of the Prior Art
It has been recognized that during rotary drilling operations, the torque applied to the drill string sometimes builds up an oscillation that has particular characteristics. It has been noted that these variations in torque are related to torsional oscillations which take place in the drill string during the drilling operation. And, two dominant frequencies have been consistently observed in output signals from a dynamic torque meter. The period of these signal variations are about 3 and 8 seconds. Heretofore, a U.S. Pat. No. 3,703,096, Nov. 21, 1972, which was reissued as U.S. Pat. No. RE. 28,436 to Vitter, Jr., et al on June 3, 1975, has suggested a system for recording the torque variations during a drilling procedure. However, that arrangement required the observation of the record thus made, and such observation had to include a reading of such record in order to make the determination as to length of time for any torque oscillations which took place.
On the other hand, the applicants' invention provides a system that has the means for direct reading, in numerical results, the time duration of an average oscillation as it occurs.